A cohort of anti-human immunodeficiency virus (HIV) positive donors and controls has been under prospective follow-up since 1985 (N Engl J Med 321:917, 1989). The cohort is now in its 14th year of follow-up. At enrollment, 182 subjects were Western blot (WB) positive, including 158 asymptomatic donors, 15 blood recipients and 9 sexual partners. A control population included 70 anti-HIV reactive donors who were WB negative and 21 who were WB indeterminate. Of the 182 WB+ subjects, 87 percent were donors, 5 percent sexual partners, and 8 percent recipients. Of the 182 WB positives, 49 are alive and in active follow- up; 58 (32 percent) are dead, of whom 54 (93 percent) died of AIDS; 75 (41 percent) are lost to follow-up (LTFU). We suspect most LTFU have succumbed to AIDS, but need access to the National Death Index to establish this: 13 of the 73 LTFU were known to have AIDS at the time they left the study. Of the 51 in active follow-up, 40 (75 percent) are males and 49 (92 percent) were detected at blood donation; 19 of 51 (37 percent) have had an AIDS defining event. Others have CD4 counts under 300, but have had a stable course even before treatment. A subset of 13 patients has exceeded 10 years of follow-up and has CD4 counts persistently more than 400 with no AIDS-defining infections and no physical abnormalities except minor adenopathy. Our goal will be to focus on this group in terms of predictive factors for long-term nonprogression. AIDS or HIV-related phenomena have not developed in any of the 21 WB indeterminate or 70 WB negative subjects. - AIDS, HIV, Blood Donors - Human Subjects